1. Field of Invention
The present invention relates to technology for a high frequency circuit that is used in mobile communication devices, for example, and to a high frequency power amplification device that uses the high frequency circuit, and relates more particularly to a high frequency circuit, to a semiconductor device, and to a high frequency power amplification device.
2. Description of Related Art
High frequency power amplifiers used in cell phones, for example, have an amplification device such as a transistor, an input matching circuit for efficiently inputting high frequency signals to the amplification device, and an output matching circuit for efficiently outputting high frequency signals from the amplification device. The matching circuits are composed of capacitors, inductors, microstrip lines, or other high frequency matching device, and are usually mounted on a circuit board as a semiconductor chip package. A semiconductor chip containing the high frequency power amplification device is also mounted on the same circuit board, rendering a high frequency power amplifier module.
As cell phones have become more functional, demand for multiband cell phones capable of transmitting various different signals and multimode cell phones capable of handling different modulation signals has risen. As known from the literature, input and output impedance matching under various frequency, output, and other conditions is necessary in order to optimize the efficiency of the high frequency power amplifier. A plurality of high frequency power amplifiers each having a matching circuit with optimized impedance is required for multiband and multimode compatibility.
One possible solution is a high frequency power amplifier that has a plurality of output pins and switches for selecting the appropriate output as described in the literature.
FIG. 18 shows an example of the related art taught in U.S. Pat. No. 5,774,017 (corresponding to Japanese Laid-open Patent Publication No. 10-65466). A single-pole, double-throw (SPDT) switch 265 is disposed to the output of the last amplification device 246. The output matching circuits 264, 266 are designed for matching signals of the two different frequencies that are amplified by the amplifier 240. The single-pole, double-throw switch 265 switches to pass the output of the amplification device 246 to the appropriate output matching circuit 264, 266.
FIG. 19 shows an example of the related art taught in Japanese Laid-open Patent Publication No. 2005-86738. A double-pole, double-throw (DPDT) switch 14 is connected to the outputs of the final amplification device 31 and the preceding amplification device. The output matching circuits 56, 56′ are designed for matching signals of the two different frequencies that are amplified by the amplifier 50. The double-pole, double-throw switch 14 can switch the two inputs to the appropriate output matching circuits 56, 56′.
A problem with the related art thus described is that because a switching device must be connected before or after the final amplification stage, the switching device increases the output loss of the amplification device.